The invention relates to a cleaning device for castings and similar components with coatings, especially for precision casting elements covered with a thin ceramic layer, with a chamber filled with water and an electrode positioned in the water, as well as the hoist that moves the components.
Various processes are used to clean castings or casting elements, some of which are tailored to the casting in question and some of which are used for all castings. For example, castings made of hard metal are cleaned by sand blasting, which is generally possible only through manual operation. Furthermore, sand blasting is possible only with hard metals, since otherwise the material being cleaned is partially worn away or else deformed. A further disadvantage is that with sand blasting only a relatively small amount of pressure can be applied in order to ensure error-free operation. Since the castings to be cleaned must be moved around in the sand blast, or the sand blasting generator must be guided around the casting element to be cleaned, the total cleaning process is very costly. There are also chemical processes in which sand and other deposits are removed chemically. Besides the current, increasingly critical problems with waste disposal, however, managing these processes is costly and demands a great deal of time, so that these processes too are used only in very limited applications. With soft metal materials such as copper and aluminum, high-pressure water is also used, whereby the water-jet systems spray water on the casting element to be cleaned at pressures of up to 500 bar. This relatively gentle treatment is advantageous, but a correspondingly high level of pressure is possible only with correspondingly hard material, so that the use of this process is also limited. In precision casting in particular, where for example several individual casting elements are cast together in a cluster using a large mold, the ceramic coating left on the casting elements or the corresponding thin layer has a very detrimental effect. Work must be undertaken with great care in order not to affect or even damage the individual casting elements. On the other hand, however, due to the hardness of the ceramic layer, it is in turn necessary to work intensively and with corresponding pressure, so that the cleaning process involves considerable problems.
For large casting elements, a high-voltage discharge in liquids is also used. One such system is described in Industrieanzeiger [Industry Gazette], No. 42, Vol. 107, 1985, pp 16 ff, as a casting cleaning device with a high-voltage discharge. With a hoist, one or more castings are lowered into a water bath until the surface is clearly below the surface of the water. An electrode submerged in the water that is agitated in the water bath specific to the component generates at intervals a highvoltage discharge over the casting elements to be cleaned, which serve at the same time as the first electrode. Because of this, shock waves are generated that use the water as the medium of transmission to remove all sand residue, so that the casting elements are metallically polished after the cleaning process. It must be noted that the casting material as well is not spared the effects of the powerful discharges of energy, since the high voltage is discharged directly at the component, whereby because of the high cost savings and the clearly reduced dust load, this established process involves significant advantages. Corresponding systems have already been used successfully in the East Bloc area in particular, as a brochure from Machino-Export USSR Moscow shows. On page 13 there, a system is depicted in which apparently several electrodes spaced at intervals from each other are positioned above the casting to be cleaned that also serves as an electrode. In order to clean both sides of this casting, it must be turned by the hoist, which requires significant additional operating time and is also very laborious. Furthermore, for three-dimensional casting elements, the success of the cleaning process is called into question, since the shock waves cannot reach all the areas of the casting element. The chamber holding the casting element and the electrodes is a rectangular or square water container that is open at the top. Furthermore, the explanations reveal that this electrohydraulic process is used only to remove the core and sandy deposits from castings. Thus far, this process has apparently not been used for precision castings, nor is it applicable, since the necessary uniform stress of the surface of the casting elements is not ensured by the shock waves. Another disadvantage of this known process is that the generated shock wave can be used only partially and to a very unsatisfactory extent, since the individual casting elements can be cleaned only one side at a time.